FIG. 1 illustrates a block diagram of a conventional battery monitoring system (BMS) 100 for monitoring multiple sets of cells 112, 114 and 116. The BMS 100 includes multiple battery monitoring units (BMUs) 102, 104 and 106 to monitor the cells 112, 114 and 116, respectively. The BMS 100 further includes a central controller 120 to communicate with the BMUs 102, 104 and 106 and control all the cells 112, 114 and 116 according to cell information from the BMUs 102, 104 and 106.
As shown in FIG. 1, each of BMUs 102, 104 and 106 includes a combined circuit of a level-shifter and a multiplexer (LS/MUX) 122 to selectively receive cell voltages, an analog-to-digital converter (ADC) 124 to convert the cell voltages to digital signals, a micro-controller (MCU) 126 to control the LS/MUX 122 and the ADC 124, a register bank 128 to store the digital signals, and an opto-coupler (OPT) 130 to communicate with the central controller 120. Moreover, each of the BMUs 102, 104 and 106 includes a digital filter (not shown in FIG. 1) for the ADC 124. Each ADC 124 needs a trimming process before monitoring the cell voltages. In other words, the BMS 100 includes multiple ADCs 124, multiple MCUs 126, multiple register banks 128, and multiple digital filters for the ADCs 124. Furthermore, the BMS 100 needs multiple trimming processes for the ADCs 124. The cost and power consumption of the BMS 100 are relatively high. The size of the printed circuit board (PCB) for the BMS 100 is also relatively large.